The focus of this proposal is to continue our investigation into how motion information is processed by infants and how that processing changes with age. It is conjectured that two functions are especially important to the early development of this process. The first concerns object perception and recognition, and the second concerns spatial orientation and perceptual guidance of the self. Although both functions rely on the processing of motion information, they depend on very different transactions between the observer and the environment. It is thus necessary to study motion processing in a variety of different contexts. Three specific problems will be addressed by the proposed research: (1) Developmental changes in the perception, recognition, and representation of biomechanical motions. A series of converging studies will investigate the relative contributions of part vs whole perception, dynamic symmetry, and the representation of the human form for explaining developmental changes in the perception of biomechanical motions. (2) Developmental changes in perception-action couplings. Biomechanical studies examining the postural control system of infants, and an analysis of the dimensionality of this dynamic system will be used to formulate a more complete understanding of postural control and its contributions to the development of reaching. (3) Developmental changes in the processing of the direction and speed of motion information. Relative changes in direction and speed are fundamental to the perception of structure and self-motion from the optic array. Experiments are proposed to investigate infants' sensitivities to this information and whether spatial and temporal integration of this information parallels developmental changes in the anatomy of the visual system. The current project is interdisciplinary in scope, and incorporates concepts and procedures from the fields of psychophysics, computational vision, biomechanics, motor control theory, and infant development. It is anticipated that the results from this project will contribute many new details to our understanding of early perceptual, cognitive, and motor development, and will also provide new benchmarks for assessing normal development in infants.